The present invention is directed to a heat-shrinkable composite foil for the manufacture of tear-resistant envelopes, particularly for pipes, cables, cable connectors and the like.
A heat-shrinkable composite foil is disclosed in British Patent Specification 1 497 051, which was the basis of German GM 75 01 913. This Patent Specification describes a heat-shrinkable, tubular coupling sleeve that is composed of a single heat-shrinkable foil and of a meltable foil layer of hot-melt glue, wherein rod-shaped inserts are provided as reinforcing elements. These reinforcing elements are embedded in the form of mechanically rigid longitudinal rods that extend transversely relative to the shrink direction of the coupling sleeve and serve the purpose of reinforcing this envelope. In this way, the reinforcement elements do not impede the shrinking process. Protection against tearing or, respectively, continued tearing in the shrink direction is, thus, indeed, established. However, no reinforcement is obtained in a direction perpendicular thereto. Since the shrinking forces are effective here and pull the envelope farther apart, there is a high risk of tearing and/or continued tearing along a direction extending perpendicular to the shrink direction.
U.S. Pat. No. 4,952,437, whose disclosure is incorporated herein by reference thereto, and European Patent Application EP 0 299 439 disclose inclusion of grid-shaped reinforcing elements with which an attempt is, likewise, made to improve the resistance of shrinkable envelopes to tearing or, respectively, continued tearing. What is problematical in these embodiments, however, is that the shrinkability may be unfavorably influenced under certain circumstances.